This invention relates to control systems for mechanical engine governors of internal combustion engines and, more particularly, to the provision of speed adjusting means for reducing the maximum controlled engine speed, as desired by the operator. In its more specific aspects, the invention relates to the provision of a variable maximum speed-idle speed mechanical governor for use on diesel engines for automotive vehicles in conjunction with a system to permit use of the governor as a road speed control for the vehicle or as a means for regulating engine speed while driving accessories when the vehicle is stationary.
It is known in the art relating to governors for internal combustion engines, particularly for compression ignition engines, to provide a mechanical governor having means for controlling the engine idle speed, as well as for preventing operation above a preset maximum speed or range or speeds. One type of governor used for such purposes has centrifugal flyweights which act through a linkage against an idle speed spring and, upon its full compression, on a high spring which controls maximum engine speed. Between the preset idle and maximum speeds, the fuel input is controlled manually by the operator of the engine or vehicle, with the speed controlling function of the governor coming into play only to prevent the engine from operating below its idle speed or above its preset maximum speed.
In certain applications, particularly vehicle applications of engines having governors of the abovementioned type, there has been a need to provide some means for automatically controlling the engine speed at an intermediate level for operating accessories that might be driven by the engine while the vehicle is stationary. Numerous arrangements have been made for accomplishing this purpose and in some cases modifications of the basic governor design have been made. While some such arrangements have been useful, it is believed that none have accomplished the desired purpose in the manner of the present invention. Further, there has been an increasing need to provide in conjunction with automotive vehicles an adjustable road speed control. In the past, this function has been accomplished by the use of a separate vehicle speed governing device.